Extraordinary rendition dates back to the Reagan years and was first used against suspected Islamists in the late 1990s.

After 9/11, it was stepped up as a means of extracting intelligence from terrorism suspects, and in subsequent years hundreds of people are believed to have been "rendered" around the world through countries such as Egypt, Jordan, Afghanistan and Morocco.

Some suspects have alleged they were tortured in the countries to which US rendition crews took them. In the words of former CIA agent Robert Baer: "If you want a serious interrogation, you send a prisoner to Jordan. If you want them to be tortured, you send them to Syria. If you want someone to disappear – never to see them again – you send them to Egypt."

In 2006, the then US secretary of state, Condoleezza Rice, insisted that the US did not and would not transfer detainees to countries where they would face torture. But that statement has been contradicted by reports from the United Nations, the European parliament and others.

Rice's comments may reflect the view of the Bush administration that waterboarding and what it referred to as other "enhanced" techniques do not amount to torture.

Although Barack Obama on entering office in 2009 declared an end to waterboarding and rendition and the closure of Guantánamo, little has changed. Waterboarding had ceased, anyway, in the latter part of the Bush administration.